Agglomerating process



March 28, 1961 B. slENKlEwicz ET AL 2,977,203

AGGLOMERATING PRocEssA Filed Aug. 27, 1958 INVENTORS BOLESLAWSIENKIEWICZ RICHARD B. KOHLER MARVIN SCHULMAN AGGLMERATIN G PROCESSBoleslaw Sieukiewicz, Pearl River, Richard B. Kohler,

Riverdale, and Marvin Schulman, Brooklyn, NX., assignors to GeneralFoods Corporation, White Plains, N.Y., a corporation of Delaware FiledAug. 27, 1958, Ser. No. 757,443

3 Claims. (Cl. 23-313) This invention relates to the agglomeration ofpowders. In particular the invention relates to the production ofagglomerates of food powders such as soluble cotte powder and likebeverage powders as well as other powdered food substances like gelatin,pectin, and confectionery powders generally.

Agglomeration of powders is being practiced today in the food industryto improve the performance of various water soluble food products. Bymeans of agglomeration, powders which would ordinarily clump and oat onthe surface of liquids, will become instantized by virtue of thetendency of agglomerates to sink in a body of liquid and break upwhereby they demonstrate improved dispersibility and greater solubilityin cold water, milk and the like. Heretofore, steam has been employed towet particles of foods in powdered form whereby the particles can beagglomerated through intimate contact of the wetted particles as theystrike one another. In general, such practices have involved theformation of a stream of product to which is introduced jets of steam atan angle to the direction of travel of the powder. Thereafter,agglomeration occurs through the turbulent action which is created byvirtue of the angle of incidence of the steam to the powder as well asthe consequent redirection and collision of powders.

While such prior practices otter improvements in the agglomeration ofpowder they leave much to be desired in more than one respect. In therst place, agglomerating procedures employing steam to wet the powdermaterial have not provided the degree of yield of agglomerates desiredsuch that there is required in most cases a subsequent classificationstep wherein unagglomerated powder is recovered and recycled foragglomeration. It would be desirable to have an agglomeration processwhich provides a very high yield of agglomerates such that the foregoingclassification and recycling steps can be substantially eliminated.

In many powdery food products such as soluble coffee and coffee-likebeverage powders noted for their solubility and ease of preparation, itis desirable to provide such powders in a darkened condition. Here tooit would be desirable to employ a process which darkens the productwhile at the same time provides a high yield for the reasons indicatedabove. Dried soluble coiee extract generally has a moisture content inthe order of 3% by weight. In providing a robust appearance to the driedsoluble extract the provision of a product having a moisture contentranging up to 3% and above would be desired. The problem of providingthis high moisture content during the agglomeration process iscompounded by difficulty in agglomerat'ing the dried powdery extract insuch a way as to oder satisfactory yield. Generally, it has been theexperience that the yield of agglomerates suers when attempts have beenmade to increase the moisture content upwardly and thereby darken theproduct.

It also becomes important, in agglomerating powdery products such assoluble coffee, not only to increase moistates Piate-nt ture content andthereby darken the beverage powder, but also to avoid such an increaseas will introduce the problem of lumping or caking upon agglomeration.

Agglomeration has also been employed in the past as a procedure forintroducing a carrier or dispersing medium with respect to a productsuch as gelatin, pectin, algin and other gums or colloids. Byinter-mixing gelatinous hydrophilic or other colloidal material withsugars such as lactose, sucrose, dextrose and'mixtures thereof toprovide an agglomerate, the product demonstrates mproved dispersion andin turn improved solubility and appearance. The factor of uniformdensity is also to be considered and the technique of agglomeration hasbeen employed to insure uniform density of material. Here again, yieldconsiderations play a significant part in the suitability of theagglomerating process for, with improved degree of agglomeration, i.e.,increased percentage of agglomerates formed, there is correspondinguniform* ity of product density.

In addition, most of the steam agglomerating procedures of the prior artrequire a subsequent drying step since, in order to recover the productin a non-tacky condition, it is generally `required that substantialmoisture be evaporated from the product. Otherwise, the agglomerate willtend to plaster the walls of the collecting charnber and lump. It wouldbe desirable to have an agglomerating process wherein drying equipmentand the accompanying capital expense involved as well as the operatingexpense of heat supply is eliminated.

The drawing is a side view showing applicants invention. Morespecifically, a plane of discretely arranged powder particles is formed(1). The plane of powder particles is then moved in a rst direction (2).A jet of steam (3) is introduced to the plane of powder particles to wetthem suiciently so that they are capable of adhering to one another whenthey contact each other. The jet of steam travels in a path (4)substantially coinciding with the plane of said powder particles and isdisposed at a substantial angle (5) to said iirst direction. The steamjet has a force suflicient to redirect the particles in said plane (6)and project them while in said plane in the path of travel of the steam.The wetter powder particles carried in the path of steam are caused tocontact one another and agglomerate (7).

Iny accordance with the present invention an improved agglomeratingprocedure is provided by forming a plane of discretely arranged powderparticles moving in a first direction, preferably in the form of afalling curtain. 'Ihe word curtain refers to a substantially planardistributionof product. A jet of steam is introduced at an anglesubstantially normal to the direction or" travel of the curtain ofproduct and may range generally from an angle of 45 to an angle of 135with respect to the direction of travel of the product, the path of thejet of steam being substantially' in the plane of the curtain of productsuch that the particles are redirected by the steam jet and wet; in thisway the particles are redirected in a single stream `substantiallycoinciding with the path of the steam jet and more or less concentratedwith respect to the locus of that jet for a long period of time as theparticles travel therealong. Thus, as the particles in the curtain enterthe path of the jet of steam they immediately become wetted and by beingdirected in the path of the steam jet are caused to contact one anothersuch that by virtue of the prolonged period wherein they are providedthe opportunity for contact or collision, a greater percentage ofagglomeration is experienced. The force of the steam jet can be adjustedso as to get utilization of the agglomeration process consistent withthe properties of the product being agglomerated but, in any event, thejet should have a force suicient to redirect the particles in thecurtain and to maintain and project the particles in a unitarypencilform path over a prolonged period of time such that the maximalopportunity for collison or contact of the wetted particles is aorded.On the other hand, the force of the steam jet should be below that pointat which turbulence renders it impossible for the particles to beredirected and collide in a single unitary path coinciding with the zoneof inuence of the steam jet. The curtain of powdery product should beintroduced to the steam jet in as thin and as wide a stream as practicalin order that the particles are suiciently separated one from anotherand can be independently redirected and bombarded with respect to oneanother in their wetted condition thereby effecting agglomeration. Thus,the particles should be suiiiciently discretely separated one from theother in a narrow plane or sheet and be disposed with respect to thedirection of the steam jet in such fashion as to be effectivelyredirected into a thin pencil-form stream wherein substantially all ofthe particles are confined as they are projected after being wetted. Theinner diameter of the steam pipe should be substantially greater thanthe thickness of the curtain of material. In general, it has been foundthat a steam pipe having an inner diameter of 1/2 to 1 inch may beemployed to agglomerate a curtain of product ranging in thickness fromas thin a stream as can possibly be curtained up to 1A inch.

The curtain of material should be disposed with respect to the outlet ofthe steam jet in such fashion that the force of the steam is effectivelyutilized in order to redirect and agglomerate the wetted particles in apencillike stream; when the curtain of material is disposed at too greata distance from the origin of the steam jet the force of the steam willbe spent and the eiciency of the operation will be correspondinglydecreased. The separation between the jet and the edge of the curtainproximate the steam jet will in large measure be determined by thevelocity of the steam as well as the width of the curtain. For curtainsof substantial widths it will generally be found practical to locate theproximate edge of the curtain as close as possible to the jet of steam.In addition, the width of the curtain should not be above that at whichthe eiect of the steam jet cannot be fully realized without sacrificinga yield of agglomerates.

In accordance with the present invention the foregoing curtain ofpowdery material can be created by any one of a number of means. Thepowder can be introduced into the steam jet from a vibrating conveyor orbelt conveyor which introduces the product 'm the form of a cascade. Or,the product can be introduced from a hopper provided with a suitablyelongated thin narrow slit through which the product may issue into thepath of a jet of steam. In lieu of a single steam .jet a plurality ofsteam jets may be employed with the appropriate number of powder streamsfeeding a corresponding number of jets.

With respect to the steam source, the degree of wetness of the steamused will be to some extent dependent upon the type of product beingagglomerated. Likewise, the pressure of the steam will be a function ofthe force of steam required which in turn is dependent upon the type ofcurtain of material being introduced thereto. In general, steam having aline pressure in the order of 15 p.s.i.g. has been found to offersatisfactory force for the purpose of redirection and agglomeration. Thescope of the invention is not to be limited to any specific steampressure since many factors must be taken into account to achieveefficient agglomeration, viz., the size of the orifice issuing the steamjet, the relationship of orifice size to the thickness of the curtain,the distance of the curtain from the orifice, the width and thinness ofthe curtain, the rate at which product is being fed to the steam jet,and the density of the individual powders being agglomerated. Ingeneral, wet or dry steam may be employed. In the case of dry steam thecooling which will be experienced as the steam is introduced to thecurtain will cause condensation of the moisture around the particles towet them and thereby effect agglomeration. However, it is generallydesirable to use a wet steam in order to use a lower ratio of steam topowder. Then too, the product itself will dictate to some extent thetemperature of the steam introduced. For many products which tend to befused by high temperatures and melt or become tacky and cause subsequentcollection problems, it will be desirable to employ a temperature belowthe fusion temperature of the product, all of which practices can befollowed and understood by the man skilled in the art.

The invention will now be more fully understood by reference to theaccompanying examples:

(1) The dried and powdered water extract of a beverage roast comprisingbran, molasses and barley and having the bulk density listed below wasfed from a chute about 5 wide in the form of a curtain 1/16-1/8 thick ata rate of approximately 45 lbs. per hour; the chute had an angle ofinclination of 60 with respect to the hori- Zontal. A jet of steam wascontinuously introduced to the falling sheet-like curtain of powder bymeans of a 1/2" inner diameter pipe, the orifice of the pipe beinglocated about 1 below the edge of the powder-feeding chute and 1l awayfrom the edge of the curtain produced by the chute. The steam jet wasdisposed at an angle of approximately with respect to the direction oftravel of the powder in the curtain and was located in the plane oftravel of the product. The steam was saturated, had a pressure rangebetween l530 p.s.i.g. and was introduced to the falling curtain at arate of approximately 30 lbs. of steam per hour. The falling particlesin the curtain were projected in the path of the steam jet by the forceof the steam in the plane of the curtain and were displaced from thecurtain a distance ranging from 2"-3 onto a belt conveyer. Theagglomerated product was not dried but was allowed to cool and set onthe conveyor for about two minutes prior to collection. The propertiesof the beverage powder prior to agglomeration were as follows:

The properties of the agglomerated product were as follows:

Particle Size Distribution Bulk Density, Moisture Color Percent GmJcc.

US Screen Size Through y Screen l 0.12 6.2% byweight.. Dark.

The agglomerated product was found to dissolve in cold water or milk inabout 1A of the time required for unaggloincrated powder. For instance,the beverage powder prior to agglomeration required about 4 to 41/2minutes to be dissolved in cold milk, whereas only one minute wasrequired in the case of the agglomerated product. The robust appearanceof the product was considerably enhanced by the darkening in coloroccurring upon agglomeration. The agglomerated product had a structuralstrength permitting it to be readily handled without substantialbreak-up into lines when subjected to normal filling and packagingoperations.

(2) A coiee surrogate was prepared by autoclaving a mixture of barley,corn syrup and starch in a hydrous reaction mixture at an elevatedtemperature until avor was produced. The supernatant liquid wasrecovered and was dried and ground. The ground product has an initialbulk density of 0.47 gm./ cc.; the powder was light brown in color. Thepowder was agglomerated in apparatus substantially the same as that ofExample 1 except that a 3A orifice was employed to provide the steam jetand the product was fed at a rate of 30 pounds per hour, the steampressure being the same as that in Example 1 and the steam rate being inthe order of 30 pounds per hour. The product prior to agglomeraton hadthe following particle size distribution:

Particle Size Distribution Bulk Density, Moisture Color Percent Gm./cc.US Screen Size Through Screen 90 0.47 weight Light Brown.

The product after agglomeration had the following particle sizedistribution:

Particle Size Distribution Bulk Density, Moisture Color Percent Gm./cc.US Screen Size Through Screen #50 25 #70 6 0.14 3% by Weight. DarkBrown.

3. Soluble colee powder was agglomerated under the conditions of Example2 and in the apparatus of Example 2. The unagglomerated coifee had thefollowing particle size distribution:

Particle Size Distribution Bulk Density, Moisture Color Percent GDL/cc.US Screen Size Through Screen #70 10o #120 96 0.52 2% by weight.. MediumBrown. #200 80 The agglomerated powder has the following particle size4. Gelatin powder of a size such that 100% passed a #60 U.S. StandardMesh Screen and having a bulk density of 0.62 gm./cc. was agglomeratedin the apparatus and under the conditions of Example 2. The agglomeratedproduct had the following particle size distribution:

Particle Size Distribution Bulk Density, Moisture Percent Gm./cc. USScreen Size Through Screen #7.. 90 0.27 3% by weight.

Although the invention has been more particularly described with respectto the food products wherein certain virtues such as appearance,uniformity of particle size, solubility and yield have been mostprominent, other nonfood products may equally lend themselves toagglomeration by the method of the present invention. For example,inorganic fertilizers which normally have a high percentage of diluentin order to eifect more uniform distribution of the fertilizer andeasier handling by the average user lend themselves notably to thisparticular procedure, The process provides a very clean, free-flowing,dust-free quality which will permit both the skilled and unskilledhandler of the product to properly distribute the fertilizer. Inaddition, there are other arts where the agglomeration process of thepresent invention may be employed. Many pharmaceuticals employ a diluentand are presently tableted and can be equally benefited by the improvedyield and uniformity of agglomeration achieved herein. In general,industrial chemicals and metals in which: (a) it is desirable to alterthe particle size; or (b) wherein decreasing the dusting which takesplace in handling particles of a very line size and pulverulentcharacter is sought; or (c) where it is desirable to alter the densityto a more useable state, will benelit from the present invention.

While the present invention has been described with particular referenceto specii'ic examples, it is not to be limited thereby, but reference isto be had to the ap pended claims for a definition of its scope.

What is claimed is:

1. The process of agglomerating powder which comprises forming a planeof discretely arranged powder particles moving in said plane in a lirstdirection, introducing a jet of steam to said plane to wet the particlestherein suiiiciently so that they are capable of adhering to one anotherwhen they contact one another, said steam jet traveling in a pathsubstantially coinciding with the plane of said particles and beingdisposed at a substantial angle to said rst direction, said steam jethaving a force sufficient to redirect said particles in said plane andproject them while in said plane in the path of travel of the steamwhereby wetted particles are caused to contact one another andagglomerate.

2. The process of agglomerating powder which comprises forming a planeof discretely arranged powder particles moving in said plane in a firstdirection, introducing a jet of steam to said plane to wet the particlestherein sufiiciently so that they are capable of adhering to one anotherwhen they contact one another, said steam iet traveling in a pathsubstantially coinciding with the plane of said particles and beingdisposed at an angle substantially normal to said iirst direction, saidsteam jet having a force suflicient toredirect said particles in saidplane and project them while in said plane in the path of travel of thesteam whereby wetted particles are caused to contact one another andagglomerate.

3. The process of agglomerating powder which comprises forming a fallingsubstantially flat curtain of discretely arranged powder particlesmoving in said plane in a first direction, introducing a jet of steam tosaid curtain to wet the particles therein suciently so that they arecapable of adhering to one another when they contact one another, saidsteam jet traveling in a path substantially coinciding with the plane ofsaid curtain and being disposed at an angle substantially normal to saidfirst direction, said steam jet having a force sut`n`cient to redirectsaid particles in said curtain and project` them while in said curtainin the path of travel of the steam whereby wetted particles are causedto contact one another and agglomerate.

References Cited in the le of this patent UNITED STATES PATENTS2,785,455 m; McElroy Mar. 19, 1957

1. THE PROCESS OF AGGLOMERATING POWDER WHICH COMPRISES FORMING A PLANEOF DISCRETELY ARRNGED POWDER PARA JET OF STEAM TO SAID PLANE TO WET THEPARTICLES THEREIN SUFFICIENTLY SO THAT THEY ARE CAPABLE OF ADHERING TOONE ANOTHER WHEN THEY CONTACT ONE ANOTHER, SAID STEAM JET TRAVELING IN APATH SUBSTANTIALLY COINCIDING WITH THE PLANE OF SAID PARTICLES AND BEINGDISPOSED AT A SUBSTANTIAL ANGLE TO SAID FIRST DIRECTION, SAID STREAM JETHAVING A FORCE SUFFICIENT TO REDIRECT SAID PARTICLES IN SAID PLANE ANDPROJECT THEM WHILE IN SAID PLANE IN THE PATH OF TRAVEL OF THE STEAMWHEREBY WETTED PARTICLES ARE CAUSED TO CONTRACT ONE ANOTHER ANDAGGLOMERATE.